[libvirt] [PATCH v2 10/15] qemu: capabilities: Add support for QMP schema introspection
Peter Krempa
pkrempa at redhat.com
Wed Nov 2 16:13:42 UTC 2016
Allow detecting capabilities according to the qemu QMP schema. This is
necessary as sometimes the availability of certain options depends on
the presence of a field in the schema.
This patch adds support for loading the QMP schema when detecting qemu
capabilities and adds a very simple query language to allow traversing
the schema and selecting a certain element from it.
The infrastructure in this patch uses a query path to set a specific
capability flag according to the availability of the given element in
the schema.
---
Notes:
v2:
- fixed typos
- added docs for one of the helper functions and changed param order
- added hint for query string format docs
src/qemu/qemu_capabilities.c | 191 ++++++++++++++++++++++
src/qemu/qemu_capabilities.h | 1 +
tests/qemucapabilitiesdata/caps_2.5.0.x86_64.xml | 1 +
tests/qemucapabilitiesdata/caps_2.6.0.ppc64le.xml | 1 +
tests/qemucapabilitiesdata/caps_2.6.0.x86_64.xml | 1 +
tests/qemucapabilitiesdata/caps_2.7.0.x86_64.xml | 1 +
6 files changed, 196 insertions(+)
diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 7a8202a..56c9deb 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -347,6 +347,7 @@ VIR_ENUM_IMPL(virQEMUCaps, QEMU_CAPS_LAST,
"machine-iommu",
"virtio-vga",
"drive-iotune-max-length",
+ "query-qmp-schema",
);
@@ -1488,6 +1489,7 @@ struct virQEMUCapsStringFlags virQEMUCapsCommands[] = {
{ "rtc-reset-reinjection", QEMU_CAPS_RTC_RESET_REINJECTION },
{ "migrate-incoming", QEMU_CAPS_INCOMING_DEFER },
{ "query-hotpluggable-cpus", QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS },
+ { "query-qmp-schema", QEMU_CAPS_QUERY_QMP_SCHEMA }
};
struct virQEMUCapsStringFlags virQEMUCapsMigration[] = {
@@ -1692,6 +1694,11 @@ static struct virQEMUCapsStringFlags virQEMUCapsObjectPropsUSBNECXHCI[] = {
{ "p3", QEMU_CAPS_NEC_USB_XHCI_PORTS },
};
+/* see documentation for virQEMUCapsQMPSchemaGetByPath for the query format */
+static struct virQEMUCapsStringFlags virQEMUCapsQMPSchemaQueries[] = {
+ { "bogus/path/to/satisfy/compiler", 0 },
+};
+
struct virQEMUCapsObjectTypeProps {
const char *type;
struct virQEMUCapsStringFlags *props;
@@ -3696,6 +3703,187 @@ virQEMUCapsInitArchQMPBasic(virQEMUCapsPtr qemuCaps,
return ret;
}
+
+/**
+ * virQEMUCapsQMPSchemaObjectGetType:
+ * @field: name of the object containing the requested type
+ * @name: name of the requested type
+ * @namefield: name of the object property holding @name
+ *
+ * Helper that selects the type of a QMP schema object or it's variant. Returns
+ * the type string on success or NULL on error.
+ */
+static const char *
+virQEMUCapsQMPSchemaObjectGetType(const char *field,
+ const char *name,
+ const char *namefield,
+ virJSONValuePtr elem)
+{
+ virJSONValuePtr arr;
+ virJSONValuePtr cur;
+ const char *curname;
+ const char *type;
+ size_t i;
+
+ if (!(arr = virJSONValueObjectGetArray(elem, field)))
+ return NULL;
+
+ for (i = 0; i < virJSONValueArraySize(arr); i++) {
+ if (!(cur = virJSONValueArrayGet(arr, i)) ||
+ !(curname = virJSONValueObjectGetString(cur, namefield)) ||
+ !(type = virJSONValueObjectGetString(cur, "type")))
+ continue;
+
+ if (STREQ(name, curname))
+ return type;
+ }
+
+ return NULL;
+}
+
+
+static virJSONValuePtr
+virQEMUCapsQMPSchemaTraverse(const char *basename,
+ char **query,
+ virHashTablePtr schema)
+{
+ virJSONValuePtr base;
+ const char *metatype;
+
+ do {
+ if (!(base = virHashLookup(schema, basename)))
+ return NULL;
+
+ if (!*query)
+ return base;
+
+ if (!(metatype = virJSONValueObjectGetString(base, "meta-type")))
+ return NULL;
+
+ /* flatten arrays by default */
+ if (STREQ(metatype, "array")) {
+ if (!(basename = virJSONValueObjectGetString(base, "element-type")))
+ return NULL;
+
+ continue;
+ } else if (STREQ(metatype, "object")) {
+ if (**query == '+')
+ basename = virQEMUCapsQMPSchemaObjectGetType("variants",
+ *query + 1,
+ "case", base);
+ else
+ basename = virQEMUCapsQMPSchemaObjectGetType("members",
+ *query,
+ "name", base);
+
+ if (!basename)
+ return NULL;
+ } else if (STREQ(metatype, "command") ||
+ STREQ(metatype, "event")) {
+ if (!(basename = virJSONValueObjectGetString(base, *query)))
+ return NULL;
+ } else {
+ /* alternates, basic types and enums can't be entered */
+ return NULL;
+ }
+
+ query++;
+ } while (*query);
+
+ return base;
+}
+
+
+/**
+ * virQEMUCapsQMPSchemaGetByPath:
+ * @query: string specifying the required data type (see below)
+ * @schema: hash table containing the schema data
+ * @entry: filled with the located schema object requested by @query
+ *
+ * Retrieves the requested schema entry specified by @query to @entry. The
+ * @query parameter has the following syntax which is very closely tied to the
+ * qemu schema syntax entries separated by slashes with a few special characters:
+ *
+ * "command_or_event/attribute/subattribute/+variant_discriminator/subattribute"
+ *
+ * command_or_event: name of the event or attribute to introspect
+ * attribute: selects whether arguments or return type should be introspected
+ * ("arg-type" or "ret-type" for commands, "arg-type" for events)
+ * subattribute: specifies member name of object types
+ * +variant_discriminator: In the case of unionized objects, select a
+ * specific case to introspect.
+ *
+ * Array types are automatically flattened to the singular type. Alternate
+ * types are currently not supported.
+ *
+ * The above types can be chained arbitrarily using slashes to construct any
+ * path into the schema tree.
+ *
+ * Returns 0 on success (including if the requested schema was not found) and
+ * fills @entry appropriately. On failure returns -1 and sets an appropriate
+ * error message.
+ */
+static int
+virQEMUCapsQMPSchemaGetByPath(const char *query,
+ virHashTablePtr schema,
+ virJSONValuePtr *entry)
+{
+ char **elems = NULL;
+
+ *entry = NULL;
+
+ if (!(elems = virStringSplit(query, "/", 0)))
+ return -1;
+
+ if (!*elems) {
+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("malformed query string"));
+ virStringFreeList(elems);
+ return -1;
+ }
+
+ *entry = virQEMUCapsQMPSchemaTraverse(*elems, elems + 1, schema);
+
+ virStringFreeList(elems);
+ return 0;
+}
+
+
+static bool
+virQEMUCapsQMPSchemaQueryPath(const char *query,
+ virHashTablePtr schema)
+{
+ virJSONValuePtr entry;
+
+ if (virQEMUCapsQMPSchemaGetByPath(query, schema, &entry))
+ return false;
+
+ return !!entry;
+}
+
+
+static int
+virQEMUCapsProbeQMPSchemaCapabilities(virQEMUCapsPtr qemuCaps,
+ qemuMonitorPtr mon)
+{
+ struct virQEMUCapsStringFlags *entry;
+ virHashTablePtr schema;
+ size_t i;
+
+ if (!(schema = qemuMonitorQueryQMPSchema(mon)))
+ return -1;
+
+ for (i = 0; i < ARRAY_CARDINALITY(virQEMUCapsQMPSchemaQueries); i++) {
+ entry = virQEMUCapsQMPSchemaQueries + i;
+
+ if (virQEMUCapsQMPSchemaQueryPath(entry->value, schema))
+ virQEMUCapsSet(qemuCaps, entry->flag);
+ }
+
+ virHashFree(schema);
+ return 0;
+}
+
+
int
virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
qemuMonitorPtr mon)
@@ -3798,6 +3986,9 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
goto cleanup;
if (virQEMUCapsProbeQMPMigrationCapabilities(qemuCaps, mon) < 0)
goto cleanup;
+ if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_QMP_SCHEMA) &&
+ virQEMUCapsProbeQMPSchemaCapabilities(qemuCaps, mon) < 0)
+ goto cleanup;
/* 'intel-iommu' shows up as a device since 2.2.0, but can
* not be used with -device until 2.7.0. Before that it
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index 6e7a855..4bb3dd1 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -381,6 +381,7 @@ typedef enum {
QEMU_CAPS_MACHINE_IOMMU, /* -machine iommu=on */
QEMU_CAPS_DEVICE_VIRTIO_VGA, /* -device virtio-vga */
QEMU_CAPS_DRIVE_IOTUNE_MAX_LENGTH, /* -drive bps_max_length = and friends */
+ QEMU_CAPS_QUERY_QMP_SCHEMA, /* query-qmp-schema command */
QEMU_CAPS_LAST /* this must always be the last item */
} virQEMUCapsFlags;
diff --git a/tests/qemucapabilitiesdata/caps_2.5.0.x86_64.xml b/tests/qemucapabilitiesdata/caps_2.5.0.x86_64.xml
index 62d42c3..bea01c7 100644
--- a/tests/qemucapabilitiesdata/caps_2.5.0.x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_2.5.0.x86_64.xml
@@ -186,6 +186,7 @@
<flag name='virtio-pci-disable-legacy'/>
<flag name='machine-iommu'/>
<flag name='virtio-vga'/>
+ <flag name='query-qmp-schema'/>
<version>2005000</version>
<kvmVersion>0</kvmVersion>
<package></package>
diff --git a/tests/qemucapabilitiesdata/caps_2.6.0.ppc64le.xml b/tests/qemucapabilitiesdata/caps_2.6.0.ppc64le.xml
index 2b147fc..baada32 100644
--- a/tests/qemucapabilitiesdata/caps_2.6.0.ppc64le.xml
+++ b/tests/qemucapabilitiesdata/caps_2.6.0.ppc64le.xml
@@ -156,6 +156,7 @@
<flag name='virtio-pci-disable-legacy'/>
<flag name='virtio-vga'/>
<flag name='drive-iotune-max-length'/>
+ <flag name='query-qmp-schema'/>
<version>2006000</version>
<kvmVersion>0</kvmVersion>
<package></package>
diff --git a/tests/qemucapabilitiesdata/caps_2.6.0.x86_64.xml b/tests/qemucapabilitiesdata/caps_2.6.0.x86_64.xml
index 1c309df..ed8f286 100644
--- a/tests/qemucapabilitiesdata/caps_2.6.0.x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_2.6.0.x86_64.xml
@@ -193,6 +193,7 @@
<flag name='machine-iommu'/>
<flag name='virtio-vga'/>
<flag name='drive-iotune-max-length'/>
+ <flag name='query-qmp-schema'/>
<version>2006000</version>
<kvmVersion>0</kvmVersion>
<package></package>
diff --git a/tests/qemucapabilitiesdata/caps_2.7.0.x86_64.xml b/tests/qemucapabilitiesdata/caps_2.7.0.x86_64.xml
index 2f168da..6ebb670 100644
--- a/tests/qemucapabilitiesdata/caps_2.7.0.x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_2.7.0.x86_64.xml
@@ -194,6 +194,7 @@
<flag name='query-hotpluggable-cpus'/>
<flag name='virtio-vga'/>
<flag name='drive-iotune-max-length'/>
+ <flag name='query-qmp-schema'/>
<version>2007000</version>
<kvmVersion>0</kvmVersion>
<package> (v2.7.0)</package>
--
2.10.2
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